Formation of complexes between aza derivatives of crown ethers and primary alkylammonium salts. Part 8. 12-Crown-4, 15-crown-5, 21-crown-7, and 24-crown-8 derivatives

Abstract

The monoaza-crown ethers (3), (4), and (5) and the diaza-crown ethers (6), ( 7), (lo), and (11) form complexes with primary alkylammonium thiocyanates in organic solvents. The diaza-15-crown-5 system (11) forms well defined 1 : 1 complexes with the cis-,cis-stereochemistry shown in ( 16) but the diaza-24-crown-8 derivative (7) forms a 2 : 1 complex (G : H ratio) with benzylammonium thiocyanate having the cis,cis,trans,trans-stereochemistry (1 7a). The diaza-24-crown-6 derivative (1 0) forms weak 1 : 1 complexes which apparently adopt the double nesting conformation (18).

Role of Chirality and Macroring in Imprinted Polymers with Enantiodiscriminative Power

“…Furthermore, the size of the macroring also influences the complexing ability of the macrocycle and subsequently the performance of the imprinted polymers. 18-Crown-6 ethers form stronger complexes with guest primary alkylammonium cations than the analogous 21-membered hosts . Hence, the binding capacity of IP3 A significantly declined (50%) compared with the corresponding 18-crown-6 derived IP2 A series (Figure ).…”

“…18-Crown-6 ethers form stronger complexes with guest primary alkylammonium cations than the analogous 21-membered hosts. 23 Hence, the binding capacity of IP3 A significantly declined (50%) compared with the corresponding 18-crown-6 derived IP2 A series (Figure 5). The IP4 and IP5 series featuring precyclization analogues of the crown ether anchors show neither appreciable imprinting nor enantioseparation factors.…”